You’ve got a rash. You quickly rule out the usual suspects: You haven’t been gardening or hiking or even picnicking, so it’s probably not a plant irritant such as poison ivy or wild parsnip; likewise, it’s probably not chiggers or ticks carrying Lyme disease; and you haven’t been swimming in a pond, which can harbor the parasite that causes swimmer’s itch.
Your rash may be coming from two hard-to-escape realities of summer: heat and sun.
The main difference between the two types of rashes is that a sun rash, like sunburn, occurs on sun-exposed skin. Heat rash occurs where the skin is covered.
The skin can feel irritated and itchy, giving rise to another common term for the syndrome – prickly heat.
The sequence – you sweat and then your sweat glands clog – is more likely to occur, says Herb Allen, a dermatologist and researcher at Drexel University in Philadelphia, “when you have too much clothing on – or too-tight clothes – or have been lying still on hospital bedsheets. There’s no air flow.”
If you get it, a heavy-duty moisturizer, especially one containing lanolin, can provide relief, Allen says. Calamine lotion or cortisone cream can also help.
While every type of skin type can get sunburned, PMLE is an allergic reaction to the sun’s ultraviolet rays. Its form varies – it can produce an itchy rash or blisters or raised red blotches – and its severity varies widely. The reaction can emerge suddenly in one place, such as on arms exposed to the sun that first warm day in April.
“The condition tends to occur in the spring or early summer,” Sheu says. “It’s too much sun, too quickly.”
Some sunscreens are better than others. Products labeled “broad-spectrum” are formulated to guard against both UVA and UVB rays. Those containing zinc or titanium oxide – these are known as physical blockers – are the best bet for people susceptible to PMLE reactions, Allen says.